About six months ago, when the oil price dipped below $40 a barrel for the first time in six years, Nicholas Samy traded in his gas-guzzling truck and bought a tiny Toyota Yaris. “Petrol is still expensive,” said Mr. Samy, an owner of a U.K. construction company, as he filled up at a Shell station in central London, where unleaded gasoline costs a bit above £1 a liter—roughly $5.50 a gallon. The lowest oil prices in a decade have yet to fully trickle down and benefit Europeans, where fuel taxes are among the highest in the world. From Belgium to Poland, Europeans are mostly driving less and buying smaller vehicles, even though gasoline prices have fallen more than 20% in some countries. Brent crude, the international benchmark, has fallen more than 70% to less than $33 a barrel, from its peak of $114 a barrel in June 2014. European […]